Gaskets essentially are used to seal and prevent leakage between two parts. Cylinder head gaskets for internal combustion engines seal the gap between the cylinder head and the cylinder block. Sealing the gap, however, can be difficult because the head, block and gasket all move due to pressure and temperature fluctuations, which results in the gasket being subjected to constant pressure changes. There are also problems due to thermal expansion and thermal contraction, which occurs when the temperatures varies in the cylinder head base. There are also multiple openings in the head and the block for cylinder bores, fluid holes and bolts holes, to name a few. The areas around these openings are known to be put under additional stresses and leakage is common.
Traditionally, a molded rubber insert is used to address gasket leakage in the areas around fluid openings. The molded rubber insert is typically made solely from an elastomeric material, which has little or no structural integrity. Due to thermal motion, resulting from hot exhaust gases, increasing combustion pressure and steep thermal swings, sheer stresses are created in this area and the molded rubber insert can tear or become over compressed and does not adequately stop the leakage. Additionally, the attack of fluids, such as coolant, water and oil, on the molded rubber insert reduces its effectiveness to set compression and also make the molded rubber inserts more susceptible to wear. Ultimately, the molded rubber insert loses its recovery potential.
There are also difficulties in attaching molded rubber inserts to a parent gasket. Difficulty exists because the attachment methods are typically manual resulting in excessive time and being subject to human error.
In view of the foregoing disadvantages of the prior art it would be advantageous for a gasket to be able to prevent or resist thermal motion to the extent that it negatively affects performance of the gasket. More specifically, it would be advantageous for a gasket to eliminate or prevent compression set and stress relaxation often seen in the prior art. It would also be advantageous for the insert to be easily attachable to a parent gasket.